1. Field of the Invention
This invention relates to window anti freezing systems, especially to motor vehicle window anti freezing systems when parked in cold weather.
2. Description of Prior Art
When a motor vehicle is parked in snowy weather, its windows, especially the windshield, are often covered by ice. A driver must remove the ice before starting driving If ice formed is thick, removing it becomes difficult. This icing problem is referred to as "parking freezing" in this paper application.
There are following basic ways to treat the above problems nowadays: 1. Anti freezing, such as using the windshield washer spray to dissolve the ice (U.S. Pat. No. 5,799,359, etc.); 2. Defrosting, including: using vehicle air-defrost systems (U.S. Pat. No. 4,549,471, etc.); rear window defrost systems (U.S. Pat. No. 4,065,848, etc.); and portable defrosters (U.S. Pat. No. 5,787,228, etc.). 3. Manual tools, such as ice-scrapers (U.S. Pat. No. 4,712,269, etc.); 4. The combinations of the above ways.
However, the "parking freezing" is still not satisfactory solved. Thin ice can be easily treated by using the washer spray and the window wipers, within a few minutes of defrosting. For removing thick ice, people have to mostly rely on the vehicle air defrost systems. A vehicle air defrost system is driven by the engine to create a hot air flow from the vents positioned in the dashboard area, to defrost the windshield and warm the driver-passenger-chamber. However, these systems generally need 15-20 minutes to basically clear the windshield when thick ice is accumulated on it. They even need the double time to clear the rear window without extra help. The most widely used rear window-defrost system is an electric heating wire-network installed in the window glass. It generally needs 15-20 minutes to melt the thick ice, too and often leaves some ice in the less warm glass regions, where the wire of the network is not positioned. The defrost process is equivalent to 10-20 mile driving, consuming 0.4-0.8 gallons of gasoline each time for an average vehicle. Even on a modest estimation, the annual fuel consumption in northern area would be very large, and a great number of useful hours are wasted.
All the above defrost systems and devices are based on a heating approach, relying the engine running and time consuming.
A different approach system, supported by a battery, was disclosed by J. Patent 58-174046. It uses a temperature sensor-switch and a time-relay to actuate vehicle wipers to wipe frost away from the windshield when the ambient temperature drops below a predetermined value, preventing frost from accumulating, while a vehicle is parked. Later, U.S. Pat. No. 5,010,289 etc. disclosed a complex system, adding a humidity switch to the system to actuates wiper to sweep when both the humidity is about 100% and the windshield reaches32F,and installing a heating element of transparent film in the window glass to evaporate the frost at the same time. However, the former system can neither sense frost, nor sense a temperature range. Actually the freezing occurs on the windshield within a temperature range (FTR), it may wider than 10-15 F, depending on the weather and the vehicle, its timing period may vary from 30' to 60', and it generally takes about one hour or more for a warm windshield to cool down to FTR. So by using the above system, a user may make a mistake to turn it or not to turn it on, and does not know how long should keep it in working if turning it on. The latter system does not reliably recognize FTR either. When the weather becomes deeply cold and windy, the temperature changes greatly cross over the windshield, the system losses its common working point, 32 F, its large heating element may need a lot of energy and may not be able to respond to the fast changes of its surface temperature synchronously.
In this application for a letter patent, the authors are presenting a new window anti freezing system, Anti-Froster, powered by a battery. It uses a temperature-range-control switch, a sweeping-time-control and a low energy optic frost-monitor, to drive and handle the vehicle wiper system to work. The temperature unit turns on the system when the window cools down to its FTR, and turns off the system when the window passes the range, realizing an accurate working time control. The monitor uses optic way to detect frost accumulating on the window glass to realize conveniently and highly reliably monitoring, compared to the previous systems. And since the working is well controlled, the energy consumption of the system is the lowest overall. Thus the present invention is an effective and reliable system for solving the "parking freezing" problem for the windshield and the rear window that has a wiper.
The present system has a subsystem consisted of the optic monitor and the sweeping control, for wiping fog and rain automatically during driving. The present invention is an automatic, multi functional window sweeping system.